Sean T. McAllister is an attorney specializing in the intersection of regulatory and corporate law, and also is an experienced commercial litigator. He has been a leader in the emerging industries of cannabis, hemp, and psychedelic medicines, but also works for established businesses in other industries like entrepreneurial recycling companies, construction, liquor licensees, and others.

Sean is licensed to practice law in Colorado and California. With over 20 years practicing law, Sean has successfully handled thousands of important cases for clients.


  • Successfully defended companies and individuals in state administrative rules violation proceedings;
  • Successfully appealed the denial of a cannabis license by the City of Boulder;
  • Represented a cannabis cultivation licensee in summary suspension case where the business was shut down and was able to get the company re-opened. No Colorado licensee had previously been summarily suspended and then re-
  • Represented a company through the first Colorado independent audit regarding alleged rules violations and resolved without the loss of license;
  • Defended a pesticide recall case where state and local regulators agreed to release holds on millions of dollars of cannabis wrongfully designated as contaminated;
  • Assisted in drafting of a USDA approved 2018 Farm Bill compliant tribal hemp plan;
  • Petitioner DEA to reconsider a negative CBD rule prior to the passage of the Farm Bill; and
  • Petitioned DEA for a manufacturer’s license to produce cannabis for clinical trials.


  • Represented an owner of a licensed grow in a breach of contract litigation, where the seller of the grow license argued our client failed to pay the purchase price. Prior to trial, the seller’s only offer was for our client to pay $900,000+ to settle the case. After trial, the judge awarded our client a $502,000+ in damages due to the seller’s breach;
  • Represented dispensary owners where growers claimed to be owed money or promised ownership in exchange for their cultivation services. The verdict came back 100% in favor of the dispensary owner;
  • Defended the nation’s first product liability case against an infused product manufacturer with a successful outcome;
  • Defended Colorado’s only federal criminal prosecution of a dispensary owner for federal money laundering/Bank Secrecy Act violations with a successful outcome;
  • Defended a cannabis company in a Proposition 65 (cancer warning) lawsuit in California;
  • Sued state regulators numerous times regarding due process violations in the administration of regulatory rules; and
  • Sued a state in order to get a Native American tribe the right to grow hemp prior to the passage of the Farm Bill.
  • Handled numerous contested commercial litigation arbitrations, including an appeal of an arbitration decision


  • Closed dozens of agreements to buy and sell business amounting to tens of millions of dollars in compliance with complex regulatory laws;
  • Helped a company negotiate and close on licensing agreements with two major celebrities;
  • Assisted companies in expanding to multiple states with intellectual property licensing agreements;
  • Helping clients understand the complex tax rules that affect the cannabis industry, including IRS Code 280E; and
  • Negotiated resolutions to disputes among business owners.

Psychedelic Law:

  • Represented therapists and doctors interested in engaging in psychedelic-assisted therapy;
  • Advised clients on what is allowed in cities that have decriminalized psychedelics;
  • Advised clients looking to obtain a religious exemption from criminal law for the use of psychedelics under the Religious Freedom Restoration Act;
  • General Counsel Decriminalize Denver campaign around psilocybin mushrooms;
  • Legal Advisor to the Decriminalize Psilocybin California 2020 campaign;
  • General Counsel to the Chacruna Institute for Psychedelic Plant Medicines; and
  • Executive Officer of the Denver Psilocybin Mushroom Policy Review Panel, 2020.
  • Legal Advisor to the Entheo Society of Washington State on a city decriminalization measure for psychedelics

Complex Criminal Law:

  • Defended Colorado’s only federal criminal prosecution of a dispensary owner for federal money laundering/Bank Secrecy Act violations with a successful outcome;
  • Defended individuals charged with felonies based on allegedly lying on applications for cannabis licenses.
  • Handled complicated felonies, including 2nd Degree Assault and sexual assault cases, through trial.
  • Represented business owners accused of felonies based on selling spice, or synthetic cannabis products.
  • Won an acquittal of a client on a vehicular homicide charge at trial.
  • Represented numerous criminal defendants accused of violating Colorado’s medical marijuana laws.

Leadership and Awards:

  • 2020 Cannabis Business Awards Cannabis Executive of the Year
  • 2017-2019, National Cannabis Industry Association, Board of Directors
  • 2018 MG Magazine, 30 Powerful Litigators You Should Know In Cannabis
  • 2016-2020 5280 Magazine, Recognized as a Top Marijuana Lawyer in Colorado
  • 2004-2012 Chairman of Board of Directors, Sensible Colorado, which assisted in drafting and running the Colorado initiative that legalized adult use cannabis in Colorado
  • 2019, 2015, and 2013 Cannabis MVP in Colorado, Cannabis Business Awards
  • 2012-2014 Spokesperson for Colorado NORML
  • 2009 Friend of Reform Award, Sensible Colorado
  • 2009 Gideon Award winner, from the Colorado Criminal Defense Bar, for his pro bono defense of protesters.

Pro Bono:

  • DUI Task Force Member, 2011-2012, Colorado Commission on Criminal and Juvenile Justice;
  • Minority Cannabis Bar Association Criminal Record Sealing event 2018;
  • Breckenridge Open Space Advisory Commission 2007-2009;
  • Breckenridge Planning Commission 2009-2010;
  • Represented protesters at the Democratic National Convention, 2008; and
  • Represented a Black Lives Matter protester, 2020.